Fortuna Mining Corp. (NYSE: FSM) (TSX: FVI) is pleased to announce an updated Mineral Resource estimate for the Diamba Sud Gold Project, effective January 16, 2026. Indicated Mineral Resources total 1.25 million ounces of gold, reflecting an increase of 530,000 ounces from the prior estimate and demonstrating open resource growth potential.

Jorge A. Ganoza, President and CEO, commented, “This updated Mineral Resource estimate represents a significant advancement for the Diamba Sud Gold Project, highlighted by a 73% increase in indicated gold ounces with 94% of total gold ounces now in the indicated category. This update provides a strong foundation for the feasibility study we plan to publish by mid‑year 2026 and materially advances the project toward a final investment decision.” Mr. Ganoza continued, “Diamba Sud, together with the expansion of the Séguéla Mine, currently under study, is central to our strategy to grow Fortuna into a company capable of producing more than 500,000 ounces of gold annually from long‑life assets.”

Updated Mineral Resource Highlights

• Total Indicated Mineral Resources of 26.0 million tonnes averaging 1.50 g/t Au, containing 1.25 million ounces of gold.
• First time estimation of Indicated Mineral Resources at the Southern Arc deposit, comprising 6.0 million tonnes averaging 1.91 g/t Au and containing 367,000 ounces of gold, establishing Southern Arc as the largest gold deposit discovered to date at Diamba Sud.
• Infill drilling successfully upgraded Inferred to Indicated Mineral Resource category at the Area D, Southern Arc, Moungoundi, and Karakara deposits, increasing resource confidence.
• Technical studies are advancing for the estimation of Mineral Reserves, with a feasibility study targeted for completion by the end of Q2 2026.
• Ongoing exploration drilling of Southern Arc, Moungoundi, and additional new targets continues to intersect mineralization beyond the current Mineral Resource envelopes, highlighting further growth potential.

Diamba Sud Gold Project – Mineral Resources by Deposit

Notes:

1. Mineral Resources are reported using the 2014 CIM Definition Standards.
2. Mineral Resources are reported insitu, on a 100% basis as of January 16, 2026. The Government of Senegal will assume a 10% free-carried ownership interest in the Project when an exploitation permit is granted, and may elect to purchase up to an additional 25% interest in Boya SA at a “fair price” as determined through an independent valuation upon the granting of the exploitation permit.
3. Mineral Resources are reported from a regularized block model derived from the original subblocked model to account for mining dilution.
4. Factors that could materially affect the reported Mineral Resources include changes in metal price and exchange rate assumptions; changes in local interpretations of mineralization; changes to assumed metallurgical recoveries, mining dilution and recovery; and assumptions as to the continued ability to access the site, retain mineral and surface rights titles, maintain environmental and other regulatory permits, and maintain the social license to operate. Boya SA has also applied for an exploitation permit and an environmental impact assessment permit for the Project. If the aforementioned permits are not granted, this will have a material impact on the potential development of the Project.
5. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.
6. Mineral Resources are reported inside constraining pit shells using selective mining unit block sizes and at an incremental gold cutoff grade for oxide/transitional material of 0.26 g/t Au, with fresh material reported based on a cutoff of 0.29 g/t Au for Area A, 0.37 g/t Au for Area D, 0.31 g/t Au for Karakara, 0.33 g/t Au for Western Splay, 0.28 g/t Au for Kassassoko, 0.31 g/t Au for Southern Arc, and 0.33 g/t Au for Moungoundi in accordance estimated average base mining costs of US$4.57/t for all material mined, average processing and G&A costs of US$21.45/t milled, and sales and transportation costs of US$7.00/oz of gold. Pit slope angles applied are 33° for weathered material and 46° for fresh rock. The long-term gold price was US$3,300/oz. Metallurgical recoveries are estimated using grade versus recovery relationship formulas developed for oxide/transition rock (all deposits) and separate formulas for fresh rock in each of the seven deposits A royalty of 3.5% has been considered in the generation of the pit shell and cut-off grade determination.
7. Eric Chapman, P. Geo. (EGBC #36328), is the Qualified Person responsible for Mineral Resources, being an employee of Fortuna Mining Corp.
8. Totals may not add due to rounding

Mineral Resources

Fortuna estimates that the Diamba Sud Gold Project contains Indicated Mineral Resources of 26.0 Mt at an average gold grade of 1.50 g/t, containing 1,254,000 ounces of gold, and Inferred Mineral Resources of 2.1 Mt at an average gold grade of 1.13 g/t containing 77,000 ounces of gold.

The updated Mineral Resource estimate incorporates drilling completed between July 2025 to January 2026. The additional data enhanced geological interpretation and resource modelling at Area A, Area D, Karakara, and Western Splay, and supported resource growth at Southern Arc and Moungoundi. Expansion drilling at Southern Arc and Moungoundi, together with drilling of new regional targets, is ongoing and is planned to continue throughout 2026, with the objective of further delineating mineralization beyond the current Mineral Resource envelopes.

Changes from the previous Mineral Resource estimate are primarily attributable to:

• Infill drilling at Area A, Area D, Karakara, Southern Arc, Moungoundi, and Western Splay, which improved geological interpretation and supported the conversion of Inferred Resources to Indicated Resources, increasing overall resource confidence.
• Expansion drilling at Southern Arc and Moungoundi resulted in increased Mineral Resources for these deposits.
• An updated gold price assumption of US$3,300 per ounce, applied in the resource estimation process.

Feasibility Study

Fortuna is progressing with the feasibility study for the Diamba Sud Gold Project to support a potential construction decision targeted for mid- 2026, with delivery of the study expected by the end of Q2 2026.

Qualified Person

Eric Chapman, Senior Vice President, Technical Services, is a Professional Geoscientist of the Association of Professional Engineers and Geoscientists of the Province of British Columbia (Registration Number 36328) and a Qualified Person as defined by National Instrument 43-101- Standards of Disclosure for Mineral Projects. Mr. Chapman has reviewed and approved the scientific and technical information contained in this news release and has verified the underlying data.

About Fortuna Mining Corp.

Fortuna Mining Corp. is a Canadian precious metals mining company with three operating mines and a portfolio of exploration projects in Argentina, Côte d’Ivoire, Mexico, and Peru, as well as the Diamba Sud Gold Project in Senegal. Sustainability is at the core of our operations and stakeholder relationships. We produce gold and silver while creating long-term shared value through efficient production, environmental stewardship, and social responsibility.